JPS63177584A - Assembly of hybrid integrated circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for assembling a hybrid integrated circuit, in which chip components are mounted on both the front and back surfaces of a circuit board, and these chip components are soldered to the circuit board all at once using a solder reflow method.

[Conventional technology]

As mentioned above, when mounting chip components on both the front and back sides of a circuit board and soldering them all at once using the solder reflow method,
In particular, in order to prevent chip components mounted on the back side of the board from falling off during the soldering process, it is necessary to temporarily hold the chip components on the board in advance. Conventionally, as this temporary fixing means, an adhesive is generally used to temporarily fix the chip component on the substrate.

[Problem that the invention seeks to solve]

However, the method of using an adhesive as a temporary fixing means for chip components on a circuit board as described above has the following problems. That is, (1) a special adhesive curing process is required in order to cure the adhesive with the chip component mounted on the substrate.

(2) If the chip components are fixed on the board with adhesive, the self-alignment effect due to the surface tension of the molten solder during the subsequent solder reflow process will be inhibited, and the finished state of the soldered parts will be unstable. .

(3) Even after soldering of chip components, the adhesive is not removed and the chip components remain fixed, so the soldering between the board and the chip components may deteriorate due to the heat cycle during product use. There is a risk that soldered parts may peel off due to thermal stress caused by the adhesive.

In addition to the above-mentioned temporary fixing method using adhesive, some methods have also been implemented in which chip components are temporarily fixed using only solder paste, but chip components mounted on the back side of the board are particularly difficult to use in the soldering reflow process. When the solder paste melts during the process, the weight of the heavy chip components may cause them to fall off, causing problems.

The object of this invention is to use a temporary fixing material that does not firmly fix chip components on a board like adhesives, but can be easily removed after soldering, to secure chip components to be mounted on the back side of the board. Assembling a low-cost and highly reliable hybrid integrated circuit that allows chip components mounted on both the front and back surfaces of the board to be soldered to the board at once by temporarily holding them in place without adversely affecting the soldering parts. The purpose is to provide a method.

[Means for solving problems]

In order to solve the above-mentioned problems, according to the present invention, there is provided a step of applying paste-like solder flux for temporarily fixing the chip component at the location on the back side of the circuit board in accordance with the location where the chip component is mounted; A process of mounting and temporarily fixing the chip components on the flux coated surface, a process of mounting the chip components on the circuit board with the surface facing upward, and a process of mounting the chip components on both the front and back sides of the circuit board in the above process. A hybrid integrated circuit is assembled through a step of soldering the chip components all at once using a solder reflow method and a step of cleaning and removing the flux.

[Effect]

By mounting the chip components on the circuit board across the paste-like solder flux layer applied to the board as described above, the chip components are stably and temporarily held in place by the adhesive force of the highly viscous flux. Become so. In addition, since flux does not harden like adhesives and remains in a paste state, it does not significantly impede the self-alignment effect of soldering parts during the soldering reflow process. Easily removed in a subsequent cleaning step.

〔Example〕

FIG. 1 is an assembly process diagram of a hybrid integrated circuit according to an embodiment of the present invention, and FIGS. 2 to 4 are assembly state diagrams at intermediate stages in the assembly process of FIG. 1a+lb is a circuit board, 1a+lb is the front and back sides of the board 1, 2 is a paste-like solder flux, 3 is a solder paste pre-printed at a predetermined location on the conductor pattern formed on both the front and back sides of the circuit board 1, 4 5 is a chip component mounted on the front side of the circuit board 1, 5 is a chip component mounted on the back side of the circuit board 1, and 5a is a connection lead of the chip component 5.

Next, to explain the method for assembling a hybrid integrated circuit, first, in step I of FIG. An appropriate amount of solder flux 2 is applied (FIG. 2). This flux 2 is applied in an automatic process, for example, by a dispenser application method.

Next, step ■ is the step mentioned above! Mount the chip component 5 on the coated surface of the flux 2, and use the adhesive force of the flux 2 to temporarily fix the chip component 5 in that position (Fig. 3). Part 5
The connecting lead 5a is in contact with the solder paste 3. Next, proceed to step (2), where the entire board is heated at a temperature of 80 to 140°C for 8 hours 1 to 20 minutes while the chip component 5 is temporarily supported.
The flux is dried by heating for about a minute to remove the alcoholic solvent contained in the flux 2, increase the viscosity of the flux, and increase the bonding force with the chip component 5. In addition, this heating and drying prevents boiling of the flux 2 and scattering of the solvent during the solder reflow process performed later, and stabilizes the chip components 5 mounted on the bottom side of the board 1 without falling off. You will be able to hold it.

Here, the circuit board 10 is turned over again, and in step (2), with the front surface 1a of the board 1 facing upward, a chip component 4 is placed on the solder paste 3 that has already been printed at a predetermined location on the board.
(Figure 4).

After the chip components 4°5 are mounted on both the front and back sides of the board 1 in the above process, in the next step V, the entire temporary assembly is carried into a reflow oven with the front surface 1a of the board 1 facing upward. Then, the chip components 4 and 5 are collectively soldered to the substrate 1 by a solder reflow method. Note that since the flux 2 maintains its adhesive strength even during this solder reflow process, the chip components mounted on the back side of the substrate 1 will not fall off due to their own weight.

After the above-mentioned soldering process, a cleaning process is carried out in the following process (2), and at the same time, the flux 2 that has temporarily held the chip component 5 is removed, including the soldering part residue. Note that this cleaning process is performed by using conventional soldering cleaning equipment as is, and the entire assembly process of the hybrid integrated circuit is completed when the soldering process is 0 or more.

〔Effect of the invention〕

As described above, according to the present invention, there are a step of applying a paste-like soldering flux for temporarily fixing the chip components to the chip component mounting position on the back side of the circuit board; There is a process of mounting and temporarily fixing chip components on top of the circuit board, a process of mounting chip components on this board with the surface of the circuit board facing upward, and a process of soldering each chip component mounted on both the front and back sides of the circuit board in the above process. A process of soldering all at once using the reflow method,
By assembling the circuit through the process of cleaning and removing the flux, the chip components can be stably held temporarily on the back side of the circuit board by utilizing the adhesive strength of the inexpensively available soldering flux. It also does not interfere with the self-alignment effect of chip components due to the surface tension of molten solder during temporary solder reflow, unlike conventional temporary fixing methods using adhesives.Furthermore, the existing soldering and cleaning equipment can be used as is. The flux can be washed and removed after soldering, and circuits can be assembled by collectively soldering chip components mounted on both the front and back sides of a circuit board without requiring complicated processes or equipment.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of the assembly process of a hybrid integrated circuit according to an embodiment of the present invention, and FIGS. 2 to 4 respectively show steps 1 to 4 in FIG. FIG. In each figure, 1: circuit board, 1a: front side of the board, 1b: back side of the board,
2: Solder flux, 3: Solder paste, 4.5
: Chip parts. Figure 1

Claims (1)

[Scope of Claims] 1) A method for assembling a hybrid integrated circuit in which chip components are mounted on both the front and back sides of a circuit board and these chip components are soldered to the board all at once using a solder reflow method, the method comprising: A step of applying paste-like solder flux to temporarily fix the chip component to the chip component mounting position on the side, a step of mounting the chip component on the surface coated with the flux and temporarily fixing the chip component, A process of mounting chip components on the board with the surface of the circuit board facing upward, a process of soldering each chip component mounted on both the front and back sides of the circuit board in the above process by a solder reflow method, and a process of cleaning the flux. 1. A method for assembling a hybrid integrated circuit, which comprises assembling a circuit through a step of removing the circuit. 2) The method for assembling a hybrid integrated circuit according to claim 1, characterized in that the flux temporarily fixing the chip components is heated and dried while the chip components are mounted on the back side of the circuit board. Assembly method.